Following the surgical removal of a hollow vessel portion, e.g. with an intestinal resection due to a tumor having affected a bowel section, the two hollow vessel portions have to be reconnected at their opened ends in such a manner that a continuous pathway is produced. This is referred to as end-to-end anastomosis. As a standard, the two opened ends are reattached to each other with clip suturing devices.
In particular with operations on the small and large intestines, leaky suture connections (suture insufficiency) occur from time to time, which are associated with a serious progress of disease and a high mortality rate, too.
Traditionally, wounds (for instance with operations) are closed by sewing them with stitches as an alternative to clips. Both techniques are relatively complex and leave foreign matter in the body at least temporarily, which may provoke allergic reactions in some cases. What is more, there is an increased risk of an accidental introduction of foreign matter, in the worst case pathogenic agents or allergens. This is why one tries to replace such methods and/or at least to use them as rarely as possible.
For preparing a surgical anastomosis, i.e. an operatively established connection between blood vessels, nerves or hollow organs as explained above, a novel technique has been developed which is the sealing of tissue with bipolar high-frequency current, the so called “Tissue Fusion Technology” (TFT). This technique does without any foreign matter staying in the body and also sterilizes the tissue during the sealing process, so that the risk of infection can be further reduced.
The tissue fusion by means of high-frequency technology (HF) is based on the denaturation of proteins which are present in many tissues. This allows to weld collagen-containing tissue. During the welding process, the tissue is heated up to temperatures above the protein denaturation temperature, and together with the intra- and extracellular matrix is converted into a gel-like state. After compression of the tissue faces, the liquefied tissue cools down to a fused mass, effecting a reliable connection of the tissue.
For the purpose of welding the hollow vessel portions, the tissue grasped between two clamping jaws is exposed to electrical current which flows between electrodes provided on the two clamping jaws. Any excess tissue which protrudes into the hollow organ is subsequently cut off as in the clip-based technology in order to obtain an undisturbed passage of the hollow organ.
For preventing the sealing or welding from breaking down, the parameters acting on the tissue have to be detected and controlled. In order to ensure this, a precise control of temperature, pressure, tissue impedance, distance and position etc. is required.
It is desirable to realize a uniform treatment of the tissue which is held between the clamping jaws, so that all zones are reliably reached and no zone is exposed to an excessively high current. To this end, it has to be ensured that the HF electrodes are uniformly spaced from each other and aligned so as to be parallel to each other.
The prior art contains clip suturing instruments in which the height of the deformed clips can be adjusted. This technology, however, cannot be directly compared with an adjustment of the surface pressure, as in this way the compression of the tissue is effected merely in indirect fashion on the basis of the difference between the thickness of the tissue and the height of the clips. Thus, the pressure exerted by the clips which have been set cannot be adjusted and can only be estimated in advance on the basis of empirical values with respect to the behavior of the respective tissue. In the course of the surgical operation, the surgeon does not receive any feedback about a possible mechanical damage of the tissue going beyond the damage inevitably occurring during setting the clips.
The following patent applications are known which describe adjustable distances for holding tissues to be stapled for circular clip suturing instruments:
EP2083710A1 discloses a cartridge arrangement for carrying a clip cartridge. The cartridge arrangement can be moved to a shooting position for setting the clips. An anvil on which the clips are set is functionally coupled to an anvil closure. The anvil closure may selectively move the anvil in a proximal direction toward the cartridge arrangement in order to clamp a part of the tissues, to be stapled, by the cartridge arrangement and the anvil. The device may further comprise an actuator which cooperates with the anvil closure in such a manner that the anvil is moved in the proximal direction to increase the clamping effect whereby the tissue is compressed between the cartridge arrangement and the anvil to a greater extent. An element intended for producing a variable load allows to preselect the pressure on the tissue between the anvil closure and the actuator before the clip is set.
EP2055246A1 discloses a surgical clip device for circular anastomoses. The device comprises a display showing the surgeon the approach between anvil and cartridge arrangement and the readiness for setting the clips. The anvil can be tilted away after the setting process in order to be able to remove the device from the hollow organ after the stapling process in an easier way.
Also EP2160984A2 discloses a surgical clip device which is comparable with the device known from EP2055246A1 with regard to the present invention.
In order to avoid tissue damage, pressure limiting means are used in instruments for minimally invasive surgery (MIC instruments).
With coagulation instruments as described here, it is possible to maintain a desired distance between the electrodes by spacers mounted on the clamping jaws. However, if the clamping jaws comprise a larger number of spacers provided thereon, as suggested e.g. in EP 1 656 901 B1, EP1 952 777 A1, EP 1 372 507 A1 or US 2004/122423 A1, it is inevitable that the spacers perforate the tissue to be treated, as the tissue is compressed under the spacers with closed clamping jaws to such an extent that there are permanent damages on the tissue. This has negative effects on the result of the sealing process.
As the spacers are further made from an electrically non-conductive material for avoiding a short-circuit between the HF electrodes, a so-called coagulation shade develops in the vicinity of said spacers, which means that the tissue portions are encapsulated in the vicinity of or under the spacers, hence are not supplied with electrical current or only to an insufficient extent, and an unsatisfactory welding of the vessel portions will occur. Furthermore, it has turned out that electrically insulating spacers of this type may readily flake off, in particular in case they are attached to the electrode e.g. by gluing, with the risk that they may find their way into the patient body possibly even unnoticed. In addition to that, the predefined electrode spacing is not ensured any more.
Therefore, modern clip suturing instruments available on the market comprise an adjustable clip height and a display to see if the “correct” clip height has been set. However, the user is not given any information on how the tissue is compressed during the setting or stapling process or otherwise stressed. This means that the user does not have any feedback about a possible mechanical damaging of the tissue. What is more, the surface pressure during setting the clips does not necessarily have to be directly related to the force exerted by the set clip, because the tissue may change around the clip after connection in particular in the event of complications. It may get swollen or become inflamed, for instance. With coagulation instruments, the adjustment of the distance between the clamping jaws which in functional view correspond to the anvil and the opposite holder (in most cases the clip cassette) of the clip-type instrument, is solved via spacers.
EP2079372A1 is deemed to represent the closest prior art. Specifically, this document discloses an apparatus comprising a cartridge assembly unit for receiving a clip magazine. An anvil is coupled to an anvil closure. The anvil closure is able to selectively move the anvil in the proximal direction toward the cartridge assembly unit to clamp a part of a tissue, to be stapled, between the cartridge assembly unit and the anvil. The device is also capable of limiting a compression of the tissue between the anvil closure and the actuator to prevent a further movement of the anvil in the proximal direction toward the cartridge assembly unit, if the predetermined compression level is reached.
In terms of circular clip suturing instruments, there are also known following documents relating to safety precautions:
US2009230170A1 discloses a surgical clip device comprising a housing, an elongated portion, a distal end piece, and a movable handle which is in a mechanical cooperation with the housing and can be moved between a first, open position and a second position approaching the distal end piece for clamping a tissue. A ratchet mechanism cooperates with the movable handle in mechanical fashion to prevent the movable handle toward the first, open position before the movable handle has reached a predetermined position.
EP2233084A1 shows a surgical clip device comprising an anvil locking system. This prevents an undesired displacement of the anvil in the axial direction.
However, comparable safety precautions in the use of HF sealing instruments are not known. Furthermore, it is not possible to readily transfer the requirements regarding the safety engineering which is due to the completely different ways of connecting the tissue.